1
Discovery of Temporal Changes
in the Torus around PSR B1509-58
Y. Yatsu, N. Kawai, T. Nakamori, & H. Nakajima
Tokyo Institute of Technology
2009 July 8th
2
Contents of this talk
 Introduction
 Data Analysis and Results
 Discussion
 Conclusion
2009 July 8th
Temporal studies of PWNe
Providing the information of plasma dynamics directly!
- Crab nebula
- Vela Pulsar
- PSR B1509-58
- G11.2-0.3
- PSR B0540-69
(Mori et al. 2004)
(Pavlov et al. 2003)
(DeLaney et al. 2006)
(Roberts et al. 2003)
(DeLuca et al. 2007)
We would like to find the temporal changes on the
torus of PSR B1509-58 as seen in the Crab nebula.
2009 July 8th
3
4
PSR B1509-58
Young and Energetic Pulsar
 D = 5.2 +/- 1.4 kpc
 P = 150 ms (tc =1700 yr)
 Lspin = 1.8 x 1037 ergs s-1
PSR B1509-58
 Surrounding Radio shell
(MSH15-52)
10 arcmin
We focused on the torus within 30” from the pulsar.
2009 July 8th
Very fine structures at the pulsar vicinity
Outer arc: 30~60”
Inner arc: ~30”
Nested tori
-Inner arc
-Outer arc
Gaensler et al. +02
DeLaney et al. +06
Inner ring
Inner Ring
R~10”
South Jet
1 arcmin
Yatsu et al. +09
5
6
Observations
ObsID
We used archive data of
four times monitoring observation.
2009 July 8th
5534
Date
2004,12,28 (T=0)
ExpTime
50 ks
5535
T = 41 days
43 ks
6116
T = 122 days
48 ks
6117
T = 294 days
46 ks
7
Region selection
 In order to investigate the torus,
the jet region was excluded.
 The funnel were divided into
vflow = c/3
Jet
Torus
2009 July 8th
Selected region
80 sectors with a width of 0.5”.
(I = 50deg)
Variations of radial profile
We searched moving features by using cross correlation function.
Surface Brightness
Radial profile
Vapp ~ 10.5 arcsec yr -1
41 days
81 days
(~ 0.86c for D=5.2 kpc)
172 days
0
5
10 15 20
25 30
Distance from the Pulsar [arcsec]
We detected moving features on the torus
running at 10.5 arcsec/yr outward from the pulsar !
2009 July 8th
8
9
Calculation of the moving velocity
Considering the superluminal motion effect,
i
Apparent Velocity [c]
v ~ 0.65c (30° < i < 50°) is required for vapp = 0.86c.
1.0
0.8
0.6
0.4
0.2
0
2009 July 8th
Vapp = 0.86c
0.2
0.4
0.6
Velocity [c]
0.8
1.0
10
What’s moving? (1)
“Actual motion of the pulsar wind”

Based on the brightness distribution of the torus
(Pelling et al. 1987)
Vflow ≤ 0.6c (for i ≥ 30 deg)

From the KC-model（Kennnel & Coroniti 1984）…
Vflow = c/3(rTS/r)2 ≤ c/3
It is difficult to explain the proper motion by the
actual flow velocity of the pulsar wind.
2009 July 8th
11
What’s moving? (2)
“Propagation of magneto-sonic wave”
Velocity of the Fast-mode magneto-sonic wave
VA  c s
2
VF =
VA =

2
1 (VA /c)
2
~ 0.7c
c
1 4 ( c  4 p)/B
1
cs 
c ~ 0.58c
3
2
2

c
1 (16U /3B )
2
= 0.63c
(Delaney et al. 2006)



2009 July 8th
The Fast mod magneto-sonic wave can explain
the observed proper motion.
12
Summary
 We studied the temporal variation on the torus around
PSR B1509-58 using Chandra.
 We found temporal changes on the torus propagating at
10.5 arcsec yr -1, analogous to the “moving wisp” as seen
in the Crab nebula.
 The observed proper motion can be explained by the
magnetosonic wave propagating at ~ 0.7c .
2009 July 8th
13
0
172 days
5
1
5
2
0
2
5
ΔT = 81 day
3
0
E [a(r)  a ] [b(r  r)  b ]
ΔT = 122 day
 a b
ΔT = 172 day
CCF
CCF(r) =
1
0
CCF
41 days
81 days
ΔT = 41 day
CCF
Radial profile
CCF
Surface Brightness
Cross Correlation Function
0
2009 July 8th
2
4
6
8
Travel Distance [arcsec]
10
Inclination angle vs Flow velocity
i=
30°
2009 July 8th
i=
40°
i=
50°
14